Just back from a week in the UKicon myself.
We visited Bletchley Park, home of the decoding efforts during WW2. We arrived mid afternoon; having driven (and Ferry) over from Paris that morning.
It's a worthwhile visit; very interesting and also slightly mindboggling! I could have done with being a bit less tired and having a bit more time to appreciate the details.

We had looked at taking a Rail holiday; Paris to London; then head North to see our friends. But the cost was just excessively expensive; so we drove.
By contrast; tomorrow I'm taking the TGV train from Paris to Bordeaux; 600kms covered in 2 hours 20 minutes for around 60 pounds! I think the UK really needs to update it's rail network.